Actually your example of Scotland vs Britain is a great example to illustrate both your comically Anglocentric view of "British" as well as your Han-centric view of "Chinese". In fact Roman Britannia NEVER referred to Scotland. It referred specifically to the Roman controlled portions of the island which did NOT include Scotland. Ever heard of Hadrian's Wall and why it was built? Read up on it some time.
I know the Romans never ruled the whole British island beyond Harian's Wall. That did not stop the Roman's to refer the whole island as Britannia, nor stop anybody west and east to use Britain to refer the whole island. Does it?
Roman Britannia never
covered land beyond the wall. That is the only sure thing one including yourself can say. Nothing more, don't stretch it. Roman rule not covering does not equate to not referring.
The right term is
Sino-centric, there is no such thing Han-centric among linguistics and historians. The difference is huge, Sino-centric includes and applies to non-Han dynasties, for example Qing is found and ruled by Manchurian emperors, not Han, but they are Sino-centric, can not be Han centric. I suspect you deliberately replaced Sino with Han is to have fact to fit your personal view. Sino is the Latin form of China, being Sino centric is being China centric, Manchu emperors being Sino centric makes them China (Chinese) centric. Doesn't it? Again defeating your equating of ethnic and statehood.
Besides Anglo-centric and Sino-centric, will you as well accuse the Swiss being Swiss centric while rejecting the German-ness, French-ness and Italian-ness? Or Austrian being Austrian-centric while the major population is German? How far are you going to accuse the whole mankind of some "centric"?
The whole foundation of your argument is that "breaking up a state along ethnic lines is a godly principle". That, I am afraid I have to say, is in principle on the edge to racism, in academics laughable, and in practice and reality disastrous.
Second, while the modern use of the word "Britain" may certainly refer to the entire island, the word "British" is certainly NOT viewed as or used as a "geographical" descriptor, but rather a national descriptor. Not only that, have you ever asked a non-English islander (Welsh, Scottish, Cornish, etc.) what he thinks about being called "British"? Of course you haven't; you just make assumptions. Here's what one Welsh politician says: "Britishness is a political synonym for Englishness which extends English culture over the Scots, Welsh, and the Irish" (Gwynfor Evans). A more perfect encapsulation of what independence-minded non-English people feel about being "British" or of potentially what Tibetans feel about being Chinese, or of how obviously clueless you are of either peoples' feelings are, I cannot imagine.
Now, you try to separate the two forms of the same word (noun and adjective) .
No, I have not asked any person from British island the question whether they identify themselves as British or English etc. because I never see a reason to ask that as I have said that question is meaningless. Haven't I?
Now, have you ever asked a Tibetan in Tibet similar question? I guess not. So
of course you just make assumptions. Please apply your logic to yourself too, that is honesty and self integrity.
The one Welsh politician who you quoted. Do you mind to give his name in your post? I hope it is not yourself? Anyway, he is like Dalai Lama who has already rejected the Britishness, in other words equates British to English only (just like you), what would I expect from him or you? Nothing.
Besides, all we are arguing back and forth can be boiled down to one question "is Statehood and Ethnical identity same thing?", my answer, many people who argues with you and the dictionaries say NO, while you insist to equate them. That is the fundamental difference between you and others, without agreeing on that, I don't see any reason for us to further argue.
The phrase "
对牛弹琴" may be harsh but not insulting in Chinese language usage, and it is absolutely accurate to describe what is between you and the rest. I can only guess two reasons that make you feel insulted, 1st Chinese is not your daily language beyond family members (I guess you are ethnic Chinese), but English is, 2nd (a sinister guess) you are probably over-sensitive, surely combative or just play victim? If you prefer, here is another phrase "chicken talks to duck" which "insults" both sides, that should be acceptable to you?